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Application rule:

Note 3 of Table 12: The first inspection of pipelines in which repair causes particular difficulties, e g. pipeline below watercourses dykes and railways, should be increased to 100%.

The initial inspection and test requirements for welds produced on site are shown in Table 12. If defects are found, the repaired section shall be inspected in accordance with Table 13.

In Table 13 the inspection is level is progressively increased, if defects are detected at the previous level of testing, from level 1 up to level 4.

Table 13 — NDT inspection levels for inspection sections where welds have been repaired on site

The test results shall be documented as specified in EN ISO 3834-2.

Application rule:

The documentation is intended to prove that the welding requirements and test provisions according to this standard are fulfilled and are traceable.

During these tests, the tested system shall be visually inspected to ensure that the system components, welds and other joints are leak tight.

Welds shall be subject to leak tightness test by one of the following methods:

1. Leak tightness test with air at 0,2 bar over-pressure or 0,65 bar below atmospheric pressure where the tightness of the weld is checked by application of a suitable indicator fluid.

2. Leak tightness test with water applied at 1,3 times the design pressure with simultaneous leak inspection of the welds.

3. 100% NTD inspection of steel service pipe when the weld seams made on site are made up of minimum 2 passes, and if starting/ending positions of the two passes are mutually displaced.

Application rule:

The leak tightness test with water can be regarded as a strength test when a pressure test is demanded. The pressure can be increased to 1,5 times the design pressure for the required period of time. Following a leak tightness test the pressure test can be performed after the pipes are buried.

The leak tightness test is compulsory and the pressure test is optional and can be specified according to local authorities or the requirements of the owner.

In project class A the leak tightness test can be done with operation pressure and the pressure test may be omitted.

The duration of a leak tightness test should be sufficiently long in order that the water can penetrate small defects e.g. pinholes.

Any pressure test shall be performed on the completed pipe section; it shall be performed on as long as possible pipe sections, on which no further work shall be done.

The test duration depends on the pipe volume and shall be agreed with the owner. A test report shall be made for each leak tightness and pressure test.

Assembly of the PE casing pipe and the insulation of joints shall be performed in accordance with the requirements of EN 489.

All types of joints shall be installed by specially trained personnel according to the instructions given by the manufacturer.

The requirements depend on the type of joint involved.

If leak detection and/or surveillance systems are part of the system, wires and other components shall be installed in the joint according to the instructions given by the manufacturer.

All joints shall be subject to a leak tightness test according to 4.1.7 of EN 489:2009, unless they are made with double sealing.

E) deleted text El

An inspection of the installed pipe shall be performed prior to backfilling of the pipe trench. This inspection involves a visual inspection of the pipe assembly, joints, expansion provisions. The registration of the as-built data such as dimensions of pipes and components and their geographical placement for registration on maps and drawings.

The pipeline area (the room between trench floor and minimum 0,1 m above top of casing pipe) shall be backfilled with the materials as specified.

During the backfilling it shall be ensured that the materials are compacted carefully around the pipes, allowing the presupposed friction between outer casing and backfill.

The backfill shall be made up in a way that neither its properties nor the compaction cause damage to pipe and joints.

The backfill material shall possess sufficient carrying capacity and the mechanical and hydraulic properties required to comply with the design basis. The backfill material shall possess such qualities that it can be compacted with a reasonable effort of compacting equipment.

Application rule:

Example of ordinary sand:

Friable, round-edged medium- or gross-grained sand, 0-4 mm.

Fine grained sand max. 8%.

The following material specification can be used for normal circumstances:

Grading: - Maximum grain size £ 32 mm

- Maximum 10% by weight s 0.075 mm

or

Maximum 3% by weight < 0,020 mm

Coefficient of uniformity: > 1,8

d10

Purity: The material should not contain harmful quantities of plant residues, humus, clay or silt lumps.

Grain form: Large keen-edged grains, which may damage pipe and joints, should be avoided.

Friction: The material composition should allow such coefficients of friction as required by the installation plan following careful compaction.

Compaction: The friction coefficients of the material are based on a standard proctor value, average 97-98%. No values below 94-95%. Careful and even compaction is required.

The subsequent backfilling of the pipe trench shall comply with the instructions for e.g. road building.

The compression zone, i.e. the room between pipeline zone and upper (e.g. road) construction shall be made from such a material and in such a manner (by layers) that the requirements made by the structures above the pipeline are fulfilled. Unsuitable material, e.g. stone and rocks, shall not be used. The upper construction zone, i.e. the room between compression zone and surface, shall be backfilled according to the instructions given by the authority responsible for the surface.

Application rule:

To reduce the risk of pipe damage by third parties it is recommended to use warning tapes, referring to the pipeline.

The warning tape shall be placed at a distance of approx. 0,2-0,5 m above the district heating pipeline.

Un-insulated pipe bends shall be installed (fitted and insulated) as specified.

Application rule:

Examples of such bends are bend fittings and specially designed bends, e g. bridges and chambers.

Special attention shall be paid to the dimensions, the installation and also the trench enlargement necessary to allow the bends (legs) to expand.

During the final inspection of the bend zone in particular, prior to backfilling, the pipeline position, thickness and length of expansion pads shall be checked to ensure that they conform to the installation plan.

The actual value of the expansions and other important pipeline measurements shall be determined prior to backfilling.

Un-insulated tees for branch lines and other types of branches shall be installed (fitted and insulated) according to the system instructions.

Application rule:

Examples of such branches are branch saddles with bend fittings and other special constructions.

In the case of branches, be especially aware that the expansion pads correspond to the specifications laid down in the installation plan.

Special attention shall be paid to the dimensions, the installation and also the trench enlargement to allow branches and or expansion legs to move as expected.

The actual value of the expansions and other important pipeline dimensions shall be determined prior to backfilling. The pipeline position, thickness and length of expansion pads shall be checked to ensure that they conform to the installation plan.

Un-insulated valves shall be installed (fitted and insulated) according to the system instructions and the installation plan.

Valves and accessories shall be installed within the stress range allowed for the specific component.

Installation of expansion pads, operating chambers, chamber covers and proper backfilling shall be performed and checked meticulously.

For the installation of chambers and covers, the instructions for road building according to installation plan shall be observed.

The proper function of the valves shall be checked before and after installation.

Application rule:

Cleaning:

The pipeline should be cleaned before it is set into operation, e g. by pigging and flushing or manual procedure.

Preservation:

If the pipelines are not set into operation immediately, preservation of the installation is recommended after a foreseeable time of standstill, e.g. using gas or liquid.

For network operation, the pipeline shall be filled with the type of water specified by the owner, and in due consideration of venting facilities at the high points.

Before the network is set in operation the backfilling of the trenches shall be completed.

While taking the network in operation the temperature rise shall be carried out with care, temperature rise shall be done slowly to allow the system to settle without sudden movement.

If leak detection and surveillance systems are installed, their function shall be checked during installation according to the manufacturers' instructions and finally after they have been set into operation.

Special components and non-standardised component shall be installed as specified.

Application rule:

Special components are, for instance:

• compensators,

• reducers,

• wall penetrations,

• fixpoints, etc.

In the existing standard the building elements (pipe, bends, accessories, sealings, valves) are intended for buried systems only. In special cases, the pipeline can be installed above ground.

The following precautionary measures shall be taken:

1. support of the pipeline,

2. protection against ultraviolet radiation.

For above-ground pipelines in particular, the static layout shall be observed.

Special attention is required for:

1. support in the tunnel,

2. avoiding damage when inserting the PE and steel pipe into the casing pipe,

3. resistance of the sealing in places where the pipes are connected to buried pipes,

4. special static conditions.

During excavation, around and close to the PE casing pipe, it shall be ensured that the pipes are not damaged.

Prior to parallel excavations, a corresponding calculation check shall be made, as the removal of the restraining soil will result in a risk of buckling, see Annex B.

If the soil cover is increased/reduced or its load changed substantially, a check of the statics is imperative.

Additional precautions according to the static specifications shall be taken in case a preinsulated pipeline is cut or equipped with branch lines.

Special safety regulations and welding instructions shall be taken into account when installing branches on pressurised pipelines, e.g. hot tapping procedure.Annex A
(normative)

Design of piping components under internal pressure

A.1 General

This annex gives rules for the determination of the required minimum wall thickness to withstand the design pressure.

When use is made of internationally standardised components designed for internal pressure according to the relevant standard recalculation according to this annex is not required.

Application rule 1:

As an alternative an equivalent national standards may be used.

The following pipe components are considered in this annex:

— straight pipes and bends,

— tees and branch connections,

— reducers and extensions, — dished ends.

Application rule 2:

Dished ends may occur as a temporary provision during hydrostatic pressure testing or as a permanent provision at the pipeline ends which will be extended in the future.

A.2 Symbols

d Diameter of service pipe

R Bend radius

t Wall thickness

z Joint efficiency factor.

CFp_d Calculated stress from design pressure

a_d Design stress = R_e(T)/ = R_e(T)/1,25

I Reinforcing length

T Design temperature

Indices:

b Branch pipe

d Design

/ Inner

m Mean, metal

о Outer

r Run pipe

p Compensating plate, pressure

A.3 Straight pipe and bends

A.3.1 Straight pipes

For straight pipes with T < 140° C the minimum wall thickness from internal design pressure shall be calculated from:

t = P^. ^do

^mm2 a_dz

tn * t_min+c,+c₂

where:

c₁ is addition for tolerance;

c₂ is addition for corrosion.

A.3.2 Bends

The minimum wall thickness for a bend shall be calculated as follows:

For the intrados (inside fibre of bend):

R-0,25d_i

'^{m,n m,n}R-0,5d_m

For the extrados (outside fibre of bend):

, R + 0,25 ■ d.

e._m,n tmin _{R + 05}

where

t_mm is the minimum wall thickness for a straight pipe according to A.3.1.

A.4 Tees and branch connections

A.4.1 General aspects and limitations

The design method specified in this paragraph shall apply to cylindrical tees and branch connections with following requirements:

1. circular openings,

2. the axis of the branch pipe perpendicular to the axis of the run pipe,

3. two adjacent openings shall have a minimum distance between their outer edges of three times the diameter of the run pipe,

4. the distance between any tee or branch connection and any other geometric discontinuity of the run pipe shall not be less than 1,0 dm of the run pipe.

A.4.2 Reinforcement

A.4.2.1 General

Tees and branch connections may be reinforced to withstand the design pressure by:

1. an increased wall thickness of the run pipe,

2. set-on welded compensating plates,

3. an increased wall thickness of the branch,

4. combination of the methods above.

If a reinforcement is provided it shall be the same in all planes through the axis of the openings or branch.

Reinforcement of openings by compensating plates is limited to a diameter ratio of d_bm/d_rm < 0,8.

Application rule:

Increasing the wall thickness of the branch as well as the use of compensating plates are less effective methods and should only be applied if it is not possible to increase the wall thickness of the run pipe.

A.4.2.2 Dissimilar material of shell and reinforcement

If the run pipe and the reinforcement consist of material with different allowable stresses and if the allowable stress of the run pipe is the lowest, this stress shall also be taken for the reinforcement.

Material for reinforcements shall be selected avoiding thermal stresses because of significant difference in thermal expansion coefficients.

A.4.2.3 Thickness ratio

The thickness ratio tt/t_r for calculation must be not greater than the value depending by d_bm/d_rm as indicated in

Table A.1.

Table A.1 — Thickness ratio for reinforcement

A.4.2.4 Calculation method for reinforcement area

Application rule:

The required reinforcement area is calculated by the method of force equilibrium between the pressure loaded area A_p and the stress loaded cross sectional area A_m, ; see Figure A.1.

After an initial estimate of the reinforcement area, the calculation may need to be repeated using a revised estimate of the reinforcement area.

A.4.2.5 Reinforcement by increased wall thickness

The reinforcement can be obtained by an increased wall thickness of the run pipe and/or branch, This reinforced wall thickness shall exist up to a maximum distance of l_r at the run pipe and l_b at the branch, measured from the edge of the opening, see Figure A.1.

Furthermore, the following condition shall be satisfied:

■ Am — A_pp_d

where

A_p is the pressure loading area

A_m is the cross sectional metal area effective for compensation of over-pressure

/ is the reinforcing length as shown by the index:

lr = у/d _m■ t_r

I b ⁼bm '

Application rule:

The actual wall thickness of the pipe is in many cases larger than t_min calculated according to A.3.1 presupposing <Tpd = <7_d. The difference can be considered to be reinforcement of the run pipe/branch.

An international or equivalent national standard may be used for selection of tees.

A.4.2.6 Reinforcement by compensating plates

Compensating plates shall have close contact with the shell. The width of compensating plate l_p considered as contributing to the reinforcement shall not exceed l_r, see Figure A.1.

The value of t_p used for the determination of A_mp shall not exceed the thickness t_r of the run pipe.

The following condition shall be satisfied:

& d (Amr A mb A mp ) — P d A p

where

A_ms and A_mp are the cross sectional areas of the run pipe and the compensating plate effective for reinforcement.

If the design stress of the compensating plate is less than the design stress of the run pipe the following condition shall be satisfied.

& d ' (A mr ⁺A mb) + & dp ' A mp — P d A p

where

Odp is the design stress of the compensating plate material.

A.5 Reducers and extensions

A.5.1 General

Reducers and extensions are called reducers for simplicity.

This clause applies to welded or un-welded concentric reducers meant to withstand the same internal pressure as the connecting pipes where:

1. the reducer and the pipe axis are on same axis of rotation,

2. the half angle, a, at the apex of the component does not exceed 30 degrees, see Figure A.2.

Application rule:

For selection of standardised reducers reference is made to ISO 3419 or a relevant national standard.

Figure A.2 — Reducer

A.5.2 Minimum wall thickness of the cone

The minimum wall thickness at any point along the length of the cone, t_Cimm, is given by:

t . - Pd ■ ^doc 1

c,m^|n2 (7_dZ COS a

where

z is the welding factor of the longitudinal weld, if any; d_oc is the outer diameter at any point along the cone;

a is the semi angle of reducer at apex.

A.5.3 Offset reducers

In case of offset reducers the connecting pipes shall have parallel centre lines offset from each other by a distance not greater than the difference of their radius. The angle a is taken as the greatest angle between conical and cylindrical part, see Figure A.3.

Key

1 Offset

Figure A.3 — Offset reducer